Development and UX from Michael Mahemoff. Maker of Player FM. Previously: Google, BT, O'Reilly author.

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Tag Archives: timezone

Writing a multi-timezone clock gadget, I found myself needing to convert timezones in Javascript. This is one uncharted area in Ajax/Javascript – unfortunately, there is no timezone library to my knowledge. Unfortunately, there’s no public JSON service to tell you what time it is right now in Tokyo either. I could create one without too much difficulty, but I’m aiming to build a self-contained gadget, which means I want it all in Javascript.

Back to first principles, ZoneInfo is incredibly thorough, but that makes it difficult to use for a single gadget. There is a wikipedia list too, but not easily parsed. (If web 3.0 is all about the semantic web, then wikipedia will hopefully become a better home for structured data too.) I then found “City Time Zones” which is a user-generated, wiki-style, approach. The problem is it doesn’t handle daylight savings, but it will do for now – the user will simply get a checkbox to say if it’s daylight savings or not. Yeah it’s a really ordinary solution, but the only one I can manage if I’m to build the gadget in a day or so.

I extracted from the ZoneInfo a simple list you might find useful. The first iteration is sorted by timezone and I’ve junked geo and other info, so you just have the timezone names, the offset, and major locations.

Yes, Tonga is 13 hours of UTC and 25 hours ahead of those little-known places that are UTC-12. In fact, Kiribati Istland (not shown here) is +14 so a day and 2 hours ahead of the others. This wasn’t meant to be easy.

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Welcome to Michael Mahemoff's blog, soapboxing on software and the web since 2004. I'm presently using HTML5 and the web to make podcasts easier to share, play, and discover at Player FM. I've previously worked at Google and Osmosoft, and built the Ajax Patterns wiki and corresponding book, "Ajax Design Patterns" (O'Reilly 2006).
For avoidance of doubt, I'm not a female, nor ever have been to my knowledge. The title of this blog alludes to English As She Is Spoke, a book so profoundly flawed it reminded me of the maturity of the software industry when this blog began in 2004. I believe the industry has become more sophisticated since then, particularly the importance of UX.
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